Ballistocardiography and flexible film sensor biomonitoring solutions
Cardiac diseases are among the most common and deadly conditions for modern humans. Therefore, effective monitoring of heart function can help detect abnormalities early, enabling timely diagnosis and treatment to save lives. In addition to traditional Electrocardiogram (ECG) monitoring, Ballistocardiography (BCG) provides further insights into the force changes caused by heartbeats, making it highly valuable for monitoring cardiac activity. Furthermore, the use of flexible film sensors to detect biological signals such as "pulse and respiration" can enhance the accuracy of physiological monitoring. This article introduces the principles of BCG and flexible thin-film sensors, along with related solutions offered by Murata.
Cardiac diseases rank among the most prevalent and life-threatening conditions affecting modern society. Effective monitoring of heart function is crucial for early detection of abnormalities, facilitating timely diagnosis and treatment that can ultimately save lives. In addition to traditional Electrocardiogram (ECG) monitoring, Ballistocardiography (BCG) offers valuable insights by measuring the force changes produced by heartbeats, making it an essential tool for assessing cardiac activity.
Moreover, the incorporation of flexible film sensor aka Picoleaf to detect biological signals such as pulse and respiration significantly enhances the accuracy of physiological monitoring. This article will explore the principles behind BCG and Picoleaf while highlighting the innovative solutions provided by Murata in this vital area of health technology.
Non-invasive and maintenance-free ballistocardiography sensors
The heart's function is one of the most critical conditions for human survival, making the monitoring of cardiac activity the best method for early detection of heart-related diseases. Currently, there are multiple ways to monitor heart function. ECG display electrical activity, cardiologists can use ultrasound to monitor valve operation and blood flow, blood pressure measurements track resulting pressure waves, and ballistocardiography (BCG) measures the heart's pumping mechanism, providing information on the timing of each heartbeat and relative stroke volume.
The advantage of ECG is its ability to detect failures in the heart's electrical activity, such as arrhythmias, signal delays, blocking, or abnormal polarization or depolarization. Its limitations include the need for electrode attachments and the lack of information about the heart's actual pumping performance.
On the other hand, BCG sensors are placed in the bed, making them non-invasive and maintenance-free, ideal for long-term nocturnal measurements. Thus, they are excellent tools for measuring recovery and sleep quality, and can reveal conditions such as potential sleep apnea or nocturnal arrhythmias. Additionally, combining BCG measurements in the bed with daytime blood pressure wave (BPW) measurements (e.g., using a wristband) enables 24/7 monitoring of cardiac and autonomic nervous system status. Non-invasive BPW measurement is a superb tool for monitoring both heart and blood vessel function.
Measuring sleep quality with Ballistocardiography
Good sleep is essential for everyone, helping to prevent various diseases and prolong life. Its positive effects extend beyond heart or blood vessels related conditions; quality sleep is also crucial for mental wellness and even cancer prevention. For the elderly, whether at home or in nursing facilities, continuous monitoring of vital signs is necessary to enhance wellness, enable independent living, improve patient safety, reduce labor and costs, and allow earlier hospital discharge with safe remote care. For athletes, recovery and quality sleep are vital for optimal training and competition performance, as the best training and recovery produce top-tier athletes.
Moreover, heart rate and respiratory parameters are excellent indicators of a person's general condition and life expectancy. They not only measure cardiac status but also reflect the overall body condition through the autonomic nervous system, signaling various pathological conditions. For example, stroke volume variation (SVV) can serve as a measure of fluid conditions.
In elderly care and independent living, nocturnal recovery is critical, making bed-based monitoring equally valuable. With BCG, data derived from measurements can be combined with other information, such as detecting behavioral changes to identify underlying issues. Quality sleep is essential for preventing many diseases and extending lifespan, and BCG offers a non-invasive method for long-term sleep quality monitoring. Additionally, BCG can help athletes and active exercisers monitor their recovery status, avoiding acute and chronic overtraining.
Contactless biomonitoring solutions for hospitals and homes
For BCG applications, Murata offers a contactless biomonitoring solution designed for use in hospitals and homes to monitor the status of individuals sleeping on a bed. It detects biological signals such as pulse, respiratory rate, and breathing time, and can determine when a person leaves the bed or analyze sleep states. This BCG solution consists of a pre-programmed microcontroller (BCGMCU-D01) and the SCL3300-D01 inclination sensor, forming a component level solution.
This innovative bed-mounted sensor leverages the principle of BCG. When the heart beats, the force of blood flowing from the aorta to the arteries generates a reactive force in the body. As a person sleeps on the bed, the bed frame subtly vibrates due to these body movements. An ultra-sensitive accelerometer captures these faint signals, and algorithms embedded in the microcontroller extract biological signals such as pulse. The BCG product enables sensor nodes to monitor various biological signals, including pulse, respiratory rate, heart rate variability (stress-related), stroke volume, and bed occupancy detection.
The BCGMCU in this solution is the second-generation BCG product with improved performance, opening new possibilities for monitoring sleepers in hospitals and homes. This product features a microcontroller pre-programmed with Murata's BCG algorithm, paired with a low-noise SCL3300 inclination sensor on the customer's PCB design. The low-integration design allows BCG measurements to be incorporated into various healthcare products.
Key features of this BCG solution include contactless measurement for continuous, disturbance-free monitoring, a reference design method enabling broad integration options, low power consumption, and a MEMS accelerometer with virtually unlimited lifetime. It is compatible with common manufacturing methods, offers an easy-to-use serial UART interface, and outputs beat to beat intervals for calculating various heart rate (HR) and heart rate variability (HRV) metrics. Target applications include hospitals, elderly care, assisted living, beat to beat interval detection, respiratory rate detection, bed occupancy monitoring, sleep quality measurement, and stress/relaxation analysis.
The BCGMCU is designed to work with the SCL3300-D01 inclinometer as part of the BCG reference design. The BCGMCU is a pre-programmed Silicon Labs EFM32PG1B100F256GM32 microcontroller, providing a simple to use serial UART interface for customer applications. Product designs should adhere to the specifications of the EFM32PG series MCU, while the SCL3300 is configured and interfaced via a pre-programmed application.
The SCL3300 is a high-performance 3-axis inclinometer with angle output, offering exceptional performance in inclination measurement. Measuring 7.6 x 8.6 x 3.3mm (W x L x H), it allows users to select from four measurement modes based on application requirements. It features ultra-low noise, high resolution (0.001°/√Hz), a flexible SPI digital interface, and superior mechanical damping characteristics. The sensor and ASIC are packaged into a 12-pin pre-molded plastic housing, ensuring reliable operation throughout its lifetime.
The SCL3300 operates in temperatures ranging from -40 to 125°C, consuming only 1.2mA of current (at a supply voltage of 3.0–3.6V). It employs proven capacitive 3D-MEMS technology and is designed, manufactured, and tested to meet high stability, reliability, and quality standards. The component delivers extremely stable output across a wide range of temperatures and vibrations and includes advanced self-diagnostic functions. It is suitable for SMD mounting and complies with RoHS and ELV directives.
The SCL3300 Inclinometer boasts high performance and robust design, making it ideal for applications requiring stability in harsh environments. Primary uses include leveling, tilt sensing, machine control, structural health monitoring, inertial measurement units (IMUs), robotics, and positioning and guidance systems.
Murata also offers a BCG reference design to assist in integrating the SCL3300 and BCGMCU into final applications. It serves as a fully tested debugger and BCG performance validation tool. The BCG reference design includes the SCL3300 inclinometer and pre-programmed BCGMCU, operates on 5–9V input voltage, and features a UART interface for data and firmware updates, along with a 40 MHz crystal oscillator.
Piezoelectric film sensors for biomonitoring applications
Murata's "Picoleaf™", enabled by proprietary piezoelectric technology, is a flexible thin-film sensor capable of highly sensitive detection of "bending," "twisting," "pressing force," and "vibration." It saves mounted space and improves upon conventional sensors in terms of thinness, assembly performance, and durability. Beyond space-saving installation, it offers features such as seamless button creation on metal casing or interaction with users in water-prone areas (e.g., bathrooms, kitchens).
The Picoleaf™ flexible film sensor is ≤0.2mm thick, enabling space-efficient integration even with displays or touchscreens. Its compact dimensions (2.5 x 7.0mm) make it ultra-small. The flexible structure allows it to conform to curved surfaces, making it suitable for high-design devices or even cylindrical shapes.
The Picoleaf™ sensor is non-pyroelectric, eliminating drift caused by body temperature, sunlight, or semiconductor heating, thereby minimizing thermal noise. It is also low-power, with zero power consumption for the sensor itself and a drive amplifier circuit designed for low current consumption (~10µA).
The Picoleaf™ sensor uses an environmentally friendly organic piezoelectric film derived from polylactic acid (PLA), a plant-derived material. As a carbon-neutral material, it does not increase atmospheric CO2 during its lifecycle—from manufacturing to disposal and decomposition—contributing to Sustainable Development Goals (SDGs). It is also lead-free, complying with the European RoHS directive.
When combined with detection circuitry, the sensor produces output based on the displacement speed of the piezoelectric film. Leveraging this output characteristic, it can serve as a sensor for press detection, grip detection, and biomonitoring applications. For pressing force detection, it functions as a UI sensor. When mounted on a stylus, it can detect hand-grip states.
The Picoleaf™ sensor offers high sensitivity, detecting minute displacements as small as 1µm. A single sensor can detect pressing pressure across an entire display surface. For biomonitoring applications, its high sensitivity enables detection of involuntary muscle tremors, grips, and pulse, making it suitable for monitoring "pulse and respiration" as a biosignal sensor.
Conclusion
As smart medical technologies advance, the Intensive Care Unit (ICU) is undergoing a digital and intelligent transformation. Through technologies like artificial intelligence, big data, the Internet of Things (IoT), and machine learning, medical teams can monitor patient conditions more precisely, improve diagnostic accuracy, and optimize treatment plans. Additionally, remote monitoring, smart decision support, and automated devices enhance medical efficiency, reduce human errors, and improve patient outcomes and safety. In the future, as technology continues to evolve and applications expand, smart hospital solutions will drive further advancements in the ICU, enabling more efficient, precise, and patient-centric critical care. The ADI smart hospital technology solutions introduced in this article represent some of the best choices for developing related applications.
Article Tags
